Scapulothoracic and Glenohumeral Joints Quiz

Scapulothoracic Joint

• The scapulothoracic joint is not a true synovial joint, but a gliding articulation between the scapula and the thoracic wall
• Movement occurs primarily through muscles that connect the scapula to the thorax and spine
• This joint plays a critical role in the wide range of motion of the shoulder
• Key motions include scapular elevation, depression, protraction, retraction, upward rotation, and downward rotation
• Scapular movement is essential for humeral movement at the glenohumeral joint.

Glenohumeral Joint

• The glenohumeral joint (GHJ) is a ball-and-socket synovial joint formed by the head of the humerus and the glenoid fossa of the scapula
• This joint permits a wide range of motion, including flexion, extension, abduction, adduction, internal rotation, and external rotation
• The articular surface of the glenoid fossa is shallow, which is compensated for by the glenoid labrum, a ring of fibrocartilage that deepens the socket.
• The rotator cuff muscles play a vital role in stabilizing the GH joint
• The GH joint's stability is a balance between mobility and stability, achieved through the combined action of muscles, ligaments, and the joint capsule

Acromioclavicular Joint

• The acromioclavicular (AC) joint is a plane synovial joint formed by the acromion process of the scapula and the clavicle
• It allows for limited gliding movements, primarily in the plane of the acromion and clavicle
• It is important for maintaining the overall shoulder complex shape and assisting with a wide range of humeral motions.
• Ligaments, including the acromioclavicular ligament and coracoclavicular ligament help stabilize the joint
• Dislocations of the AC joint can occur from direct trauma.

Sternoclavicular Joint

• The sternoclavicular (SC) joint is a saddle synovial joint connecting the medial end of the clavicle with the manubrium of the sternum
• This joint allows for a limited range of movement, including protraction, retraction, elevation, and depression of the clavicle and scapula
• The SC joint plays a critical role in transmitting forces between the upper extremity and the axial skeleton
• It is more stable than the GHJ due to strong ligaments such as the anterior and posterior sternoclavicular ligaments.

Shoulder Ligaments (General)

• Ligaments provide essential support to the complex shoulder structures
• The various ligaments of the shoulder girdle, although numerous, act to stabilize the joints

GH Joint Ligaments

• Glenohumeral ligaments (superior, middle, and inferior) provide significant support to the GH joint
• These ligaments resist excessive translation forces and contribute to shoulder stability.

AC Joint Ligaments

• The AC joint is stabilized by the acromioclavicular ligament and coracoclavicular ligament (conoid and trapezoid ligaments)
• These ligaments limit the range of movement between the acromion and clavicle and prevent excessive displacement of the clavicle.

Other Important Shoulder Ligaments

• Other ligaments, including the coracoacromial ligament, play a supportive role in the shoulder complex.
• Any injury to these ligaments can greatly affect shoulder function and range of motion.